、。
Back then, there weren't any native English teachers at any public school.
Literal
That period, any [gen-の] public [gen-の] school [in-any-にも] native [gen-の] English [gen-の] teacher [etc-など] didn't-exist.
Two negative-scope markers work together here: どこの ... にも ('in any / not any') and ~など ('things like X') in a negative context, giving 'not so much as native English teachers' — a dismissive/downplaying nuance. 当時 ('at that time') is a crisp single-word time expression common in narrative writing. The sentence is polite past negative (いませんでした) in a written/reflective register. The stacked の chain 公立の学校にも indicates 'even at any public school.'